Heat treatment is a requisite procedure for a semiconductor process, and is required in ohmic contact alloying, ion-implantation damage annealing, dopant activation, thin film formation such as TiN, TiSi2, CoSi2, and the like.
Such heat treatment may be performed using apparatuses such as a furnace and a rapid thermal process (RTP) apparatus. To date, an apparatus for a rapid thermal process is not attractive since it has difficulties in maintaining a uniform temperature across a substrate, in maintaining the same temperature-time property between substrates when a substrate (wafer) is changed, or in measuring and controlling temperature of a substrate. However, a recent advance in temperature measurement and control techniques promotes the replacement of a furnace by a rapid thermal apparatus.
A rapid thermal apparatus transfers heat to a substrate using radiant light from a tungsten halogen lamp. Therefore, such a rapid thermal apparatus has a heater block, and a plurality of tungsten halogen lamps are provided on one side faced with a substrate among sides of the heater block. A uniform temperature should be maintained throughout a substrate even when a rapid thermal apparatus is used, because a ununifom temperature of substrate causes severe problems such as substrate warpage, dislocation, thin film slip, and the like.
To solve such a temperature uniformity problem, a technique for measuring and controlling accurately a substrate temperature, a technique for transferring uniform heat across a substrate and the like are required. A technique for transferring uniform heat across a substrate is associated with an arrangement of tungsten halogen lamps. Numerous techniques associated with an arrangement of tungsten halogen lamps have been known. For example, KR Patent No. 1031226 discloses a concentric arrangement and a tessellated arrangement of lamps irradiating radiant light on a substrate.